Metal gate structure and methods thereof

ABSTRACT

Provided is a metal gate structure and related methods that include forming a first fin and a second fin on a substrate. In various embodiments, the first fin has a first gate region and the second fin has a second gate region. By way of example, a metal-gate line is formed over the first and second gate regions. In some embodiments, the metal-gate line extends from the first fin to the second fin, and the metal-gate line includes a sacrificial metal portion. In various examples, a line-cut process is performed to separate the metal-gate line into a first metal gate line and a second gate line. In some embodiments, the sacrificial metal portion prevents lateral etching of a dielectric layer during the line-cut process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/438,398, filed Dec. 22, 2016, the entirety of which is incorporatedby reference herein.

BACKGROUND

The electronics industry has experienced an ever increasing demand forsmaller and faster electronic devices which are simultaneously able tosupport a greater number of increasingly complex and sophisticatedfunctions. Accordingly, there is a continuing trend in the semiconductorindustry to manufacture low-cost, high-performance, and low-powerintegrated circuits (ICs). Thus far these goals have been achieved inlarge part by scaling down semiconductor IC dimensions (e.g., minimumfeature size) and thereby improving production efficiency and loweringassociated costs. However, such scaling has also introduced increasedcomplexity to the semiconductor manufacturing process. Thus, therealization of continued advances in semiconductor ICs and devices callsfor similar advances in semiconductor manufacturing processes andtechnology.

Multi-gate devices have been introduced in an effort to improve gatecontrol by increasing gate-channel coupling, reduce OFF-state current,and reduce short-channel effects (SCEs). One such multi-gate device thathas been introduced is the fin field-effect transistor (FinFET). TheFinFET gets its name from the fin-like structure which extends from asubstrate on which it is formed, and which is used to form the FETchannel. FinFETs are compatible with conventional complementarymetal-oxide-semiconductor (CMOS) processes and their three-dimensionalstructure allows them to be aggressively scaled while maintaining gatecontrol and mitigating SCEs. In addition, metal gate electrodes havebeen introduced as a replacement to polysilicon gate electrodes. Metalgate electrodes provide a number of advantages over polysilicon gateelectrodes such as avoidance of the polysilicon depletion effect,work-function tuning by selection of appropriate gate metal(s), as wellas other benefits. By way of example, a metal gate electrode fabricationprocess may include a metal layer deposition followed by a subsequentmetal layer cut process. In some cases, the metal layer cut process mayresult in loss of portions of an inter-layer dielectric (ILD), leadingto degraded device reliability.

Thus, existing techniques have not proved entirely satisfactory in allrespects.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is perspective view of an embodiment of a FinFET device accordingto one or more aspects of the present disclosure;

FIG. 2 is a top-view of neighboring fins, a metal gate structure, and ametal gate cut pattern, in accordance with some embodiments;

FIG. 3 illustrates a cross-section view of a FinFET structure, in whicha metal gate line-cut process is performed, in accordance with at leastsome existing processes;

FIG. 4 illustrates a cross-section view of a FinFET structure, in whicha metal gate line-cut process is performed, in accordance withembodiments of the present disclosure;

FIG. 5 is a flow chart of a semiconductor manufacturing method,according to one or more aspects of the present disclosure;

FIGS. 6A, 7A, 8A, 9A, 10A, 11A, and 12A show cross-section views of aFinFET structure along a plane substantially parallel to a plane definedby section CC′ of FIG. 1, and fabricated according to the method of FIG.5; and

FIGS. 6B, 7B, 8B, 9B, 10B, 11B, and 12B show cross-section views of theFinFET structure along a plane substantially parallel to a plane definedby section AA′ of FIG. 1, and fabricated according to the method of FIG.5.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

It is also noted that the present disclosure presents embodiments in theform of multi-gate transistors or fin-type multi-gate transistorsreferred to herein as FinFET devices. Such a device may include a P-typemetal-oxide-semiconductor FinFET device or an N-typemetal-oxide-semiconductor FinFET device. The FinFET device may be adual-gate device, tri-gate device, bulk device, silicon-on-insulator(SOI) device, and/or other configuration. One of ordinary skill mayrecognize other embodiments of semiconductor devices that may benefitfrom aspects of the present disclosure. For example, some embodiments asdescribed herein may also be applied to gate-all-around (GAA) devices,Omega-gate (Ω-gate) devices, or Pi-gate (Π-gate) devices.

The present application is generally related to a metal gate structureand related methods. In particular, the present disclosure is directedto a metal gate cut process and related structure. Metal gate electrodeshave been introduced as a replacement to polysilicon gate electrodes.Metal gate electrodes provide a number of advantages over polysilicongate electrodes such as avoidance of the polysilicon depletion effect,work-function tuning by selection of appropriate gate metal(s), as wellas other benefits. By way of example, a metal gate electrode fabricationprocess may include a metal layer deposition followed by a subsequentmetal layer cut process. In some cases, the metal layer cut process mayresult in loss of portions of an inter-layer dielectric (ILD), leadingto degraded device reliability.

Embodiments of the present disclosure offer advantages over the existingart, though it is understood that other embodiments may offer differentadvantages, not all advantages are necessarily discussed herein, and noparticular advantage is required for all embodiments. Generally, and inaccordance with embodiments disclosed herein, a metal gate cut processand related structure are provided. At least some embodiments of thepresent disclosure may be used to reduce inter-layer dielectric (ILD)loss during a metal gate cut process. For example, in at least someexisting processes, over-etching of a metal gate layer (e.g., during ametal gate cut process) may lead to such undesirable ILD loss. Tomitigate this issue, embodiments of the present disclosure provide ametal gate layer, or multiple layers, having different thicknesses on afin (e.g., FinFET) and on a neighboring line-cut region. Moreover, in atleast some embodiments, a sacrificial metal portion may be used toprevent lateral etching during a metal line cut process, therebyeffectively preventing ILD loss.

Illustrated in FIG. 1 is a FinFET device 100. Various embodimentsdisclosed herein may be used to fabricate the FinFET device 100 and/ormay be present in the final structure of the FinFET device 100. TheFinFET device 100 includes one or more fin-based, multi-gatefield-effect transistors (FETs). The FinFET device 100 includes asubstrate 102, at least one fin element 104 extending from the substrate102, isolation regions 106, and a gate structure 108 disposed on andaround the fin-element 104. The substrate 102 may be a semiconductorsubstrate such as a silicon substrate. The substrate may include variouslayers, including conductive or insulating layers formed on asemiconductor substrate. The substrate may include various dopingconfigurations depending on design requirements as is known in the art.The substrate may also include other semiconductors such as germanium,silicon carbide (SiC), silicon germanium (SiGe), or diamond.Alternatively, the substrate may include a compound semiconductor and/oran alloy semiconductor. Further, in some embodiments, the substrate mayinclude an epitaxial layer (epi-layer), the substrate may be strainedfor performance enhancement, the substrate may include asilicon-on-insulator (SOI) structure, and/or the substrate may haveother suitable enhancement features.

The fin-element 104, like the substrate 102, may comprise silicon oranother elementary semiconductor, such as germanium; a compoundsemiconductor including silicon carbide, gallium arsenide, galliumphosphide, indium phosphide, indium arsenide, and/or indium antimonide;an alloy semiconductor including SiGe, GaAsP, AlInAs, AlGaAs, InGaAs,GaInP, and/or GaInAsP; or combinations thereof. The fins 104 may befabricated using suitable processes including photolithography and etchprocesses. The photolithography process may include forming aphotoresist layer (resist) overlying the substrate (e.g., on a siliconlayer), exposing the resist to a pattern, performing post-exposure bakeprocesses, and developing the resist to form a masking element includingthe resist. In some embodiments, pattering the resist to form the makingelement may be performed using an extreme ultraviolet (EUV) lithographyprocess or an electron beam (e-beam) lithography process. The maskingelement may then be used to protect regions of the substrate while anetch process forms recesses into the silicon layer, thereby leaving anextending fin 104. The recesses may be etched using a dry etch (e.g.,chemical oxide removal), a wet etch, and/or other suitable processes.Numerous other embodiments of methods to form the fins 104 on thesubstrate 102 may also be used.

Each of the plurality of fins 104 also include a source region 105 and adrain region 107 where the source/drain regions 105, 107 are formed in,on, and/or surrounding the fin 104. The source/drain regions 105, 107may be epitaxially grown over the fins 104. A channel region of atransistor is disposed within the fin 104, underlying the gate structure108, along a plane substantially parallel to a plane defined by sectionBB′ of FIG. 1. In some examples, the channel region of the fin includesa high-mobility material such as germanium, as well as any of thecompound semiconductors or alloy semiconductors discussed above and/orcombinations thereof. High-mobility materials include those materialswith an electron mobility greater than silicon. For example, higher thanSi which has an intrinsic electron mobility at room temperature (300 K)of around 1350 cm²/V−s and a hole mobility of around 480 cm²/V−s.

The isolation regions 106 may be shallow trench isolation (STI)features. Alternatively, a field oxide, a LOCOS feature, and/or othersuitable isolation features may be implemented on and/or within thesubstrate 102. The isolation regions 106 may be composed of siliconoxide, silicon nitride, silicon oxynitride, fluorine-doped silicateglass (FSG), a low-k dielectric, combinations thereof, and/or othersuitable material known in the art. In an embodiment, the isolationstructures are STI features and are formed by etching trenches in thesubstrate 102. The trenches may then be filled with isolating material,followed by a chemical mechanical polishing (CMP) process. However,other embodiments are possible. In some embodiments, the isolationregions 106 may include a multi-layer structure, for example, having oneor more liner layers.

The gate structure 108 includes a gate stack having an interfacial layer110 formed over the channel region of the fin 104, a gate dielectriclayer 112 formed over the interfacial layer 110, and a metal layer 114formed over the gate dielectric layer 112. The interfacial layer 110 mayinclude a dielectric material such as silicon oxide layer (SiO₂) orsilicon oxynitride (SiON). The interfacial layer 110 may be formed bychemical oxidation, thermal oxidation, atomic layer deposition (ALD),chemical vapor deposition (CVD), and/or other suitable method. The gatedielectric layer 112 may include a high-k dielectric layer such ashafnium oxide (HfO₂). Alternatively, the high-k dielectric layer mayinclude other high-k dielectrics, such as TiO₂, HfZrO, Ta₂O₃, HfSiO₄,ZrO₂, ZrSiO₂, combinations thereof, or other suitable material. In stillother embodiments, the gate dielectric layer may include silicon dioxideor other suitable dielectric. The dielectric layer may be formed by ALD,physical vapor deposition (PVD), oxidation, and/or other suitablemethods. The metal layer 114 may include a conductive layer such as W,TiN, TaN, WN, Re, Ir, Ru, Mo, Al, Co, Ni, combinations thereof, and/orother suitable compositions. In some embodiments, the metal layer 114may include a first metal material for N-type FinFETs and a second metalmaterial for P-type FinFETs. Thus the FinFET device 100 may include adual work-function metal gate configuration. For example, the firstmetal material (e.g., for N-type devices) may include metals having awork function substantially aligned with a work function of thesubstrate conduction band, or at least substantially aligned with a workfunction of the conduction band of the channel region of the fin 104.Similarly, for example, the second metal material (e.g., for P-typedevices) may include metals having a work function substantially alignedwith a work function of the substrate valence band, or at leastsubstantially aligned with a work function of the valence band of thechannel region of the fin 104. Thus, the metal layer 114 may provide agate electrode for the FinFET device 100, including both N-type andP-type FinFET devices 100. In some embodiments, the metal layer 114 mayalternately include a polysilicon layer. The metal layer 114 may beformed using PVD, CVD, electron beam (e-beam) evaporation, and/or othersuitable process. In some embodiments, sidewall spacers are formed onsidewalls of the gate structure 108. The sidewall spacers may include adielectric material such as silicon oxide, silicon nitride, siliconcarbide, silicon oxynitride, or combinations thereof.

Referring now to FIG. 2, illustrated therein is a top-view ofneighboring fins 204 and a metal gate structure 208 disposed over andsubstantially perpendicular to the fins 204. In some embodiments,section AA′ of FIG. 2 may be substantially parallel to the plane definedby section AA′ of FIG. 1, and section CC′ of FIG. 2 may be substantiallyparallel to the plane defined by section CC′ of FIG. 1. In some cases,the fins 204 may be substantially the same as fins 104 described above,and the metal gate structure 208 may be similar in at least some aspectsto the gate structure 108 described above. By way of example, FIG. 2also shows a metal gate cut pattern 210, which in some examples may bedefined by a patterned hard mask layer. In some embodiments, the metalgate cut pattern 210 provides an opening (e.g., in the patterned hardmask layer) through which a metal gate line-cut process is performed andin which a portion 212 of a metal gate layer of the metal gate structure208 may be cut. A metal gate line-cut process, as described herein, mayinclude a dry etch process, a wet etch process, or a combinationthereof, which is used to remove a portion of the metal gate layer ofthe metal gate structure 208 within an area defined by the metal gatecut pattern 210. By way of example, the metal gate line-cut process maybe used to cut a metal gate line into separate, electricallydisconnected lines. In some embodiments, a dielectric layer may beformed within a line-cut region (e.g., where the portion of the metalgate layer has been removed) as part of the metal gate line-cut process.

With reference to FIG. 3, illustrated therein is a cross-section view ofa FinFET structure 300, along a plane substantially parallel to a planedefined by section AA′ of FIG. 1, in which a metal gate line-cut processis performed, in accordance with at least some existing processes. TheFinFET structure 300 may include one or more of the features describedabove with reference to the FIG. 1 such as fin elements 304 extendingfrom a substrate, isolation regions 306, and a gate structure 308disposed on and around the fin-elements 304. The gate structure 308 mayinclude a gate stack having a dielectric layer 310, including aninterfacial layer and a gate dielectric layer, and a metal layer formedover the dielectric layer 310. In some examples, the metal layer mayinclude a first metal material 312 (e.g., such as a P-type work functionmetal (PWFM)), a second metal material 314 (e.g., such as an N-type workfunction metal (NWFM)) over the first metal material 312, and a thirdmetal material 316 (e.g., such as tungsten) over the second metalmaterial 314. In various examples, a dielectric layer 318 may be formedover the third metal material 316. As also illustrated in FIG. 3, atotal thickness of the first and second metal materials 312, 314 isdefined as ‘T1’. In at least some existing metal gate line-cutprocesses, the thickness of the first and second metal materials 312,314 can lead to processing challenges. For example, FIG. 3 further showsa metal gate cut region 320, where the metal layers of the gatestructure 308 are disconnected, and which may be formed as part of ametal gate line-cut process as described above. In various cases, at asubsequent processing step, a dielectric layer may be formed within themetal gate cut region 320. Of particular note, the first and secondmetal materials 312, 314 may have a substantially uniform thickness T1extending from the fin-elements 304 to the cut region 320. Before thecut region 320 is formed, in some cases, the first and second metalmaterials 312, 314 may have a substantially uniform thickness T1extending through the cut region 320 as well, and which may be removedduring a line-cut process. In some cases, due at least in part to thethickness T1 of the first and second metal materials 312, 314 at the cutregion 320, at least some existing processes may require significantover etching of the metal layers within the cut region 320, during themetal gate line-cut process to fully remove the metal layers disposedtherein. As a result of such over etching, there may be significant loss(e.g., etching) of a nearby dielectric layer (e.g., the dielectric layer318, or other interlayer dielectric). Thus, it would be desirable toreduce such dielectric loss during the metal gate line-cut process.

Referring now to FIG. 4, illustrated therein is a cross-section view ofa FinFET structure 400, along a plane substantially parallel to a planedefined by section AA′ of FIG. 1, in which a metal gate line-cut processis performed, in accordance with various embodiments of the presentdisclosure. Generally, embodiments of the present disclosure may providea metal gate layer, or multiple layers, having different thicknesses ona fin-element of a FinFET as compared to a neighboring line-cut region.Additionally, some embodiments provide a sacrificial metal portion maybe used to prevent lateral etching during a metal line cut process. TheFinFET structure 400 may include one or more of the features describedabove with reference to the FIGS. 1 and 3 such as fin elements 404extending from a substrate, isolation regions 406, and a gate structure408 disposed on and around the fin-elements 404. The gate structure 408may include a gate stack having a dielectric layer 410, including aninterfacial layer and a gate dielectric layer, and a metal layer formedover the dielectric layer 410. As described above, the metal layer mayinclude a first metal material 412 (e.g., a PWFM), a second metalmaterial 414 (e.g., an NWFM), and a third metal material 416 (e.g., suchas tungsten). In various examples, a dielectric layer 418 may be formedover the third metal material 416. FIG. 4 also shows a metal gate cutregion 420, which may be formed as part of a metal gate line-cut processas described above, and within which a dielectric layer may be formedduring a subsequent stage of processing.

Contrary to at least some existing process (e.g., FIG. 3), and in someembodiments, the first and second metal materials 412, 414 may not havea substantially uniform thickness T1 extending from the fin-elements 404to the cut region 420. Rather, in some embodiments, the first and secondmetal materials 412, 414 may have a total thickness ‘T1’ over thefin-elements 404, as shown in FIG. 4, while having a second thickness‘T2’ less than T1 at the neighboring cut region 420. In someembodiments, the metal gate cut process used to form the cut region 420may be performed prior to deposition of the second metal material 414.In some embodiments, the thickness T2 corresponds to the thickness ofsolely the first metal material 412 (e.g., the PWFM). Therefore, in somecases, before the cut region 420 is formed, the second metal material414 may not be deposited at the cut region 420. As such, in someembodiments, the first metal material having thickness T2, and not thefirst and second metal materials having thickness T1, may be removedduring a line-cut process. In some embodiments, due to the thinner T2(e.g., as compared to T1) of solely the first metal material 412 at thecut region 420, embodiments of the present disclosure may not requirethe significant over etching of the metal layers within the cut region320, as is the case for at least some existing processes. Thus, loss(e.g., via etching) of a nearby dielectric layer (e.g., the dielectriclayer 318, or other interlayer dielectric) can be avoided. Moreover, insome embodiments, the third metal material 416 may include a materialsuch as tungsten (W), which may be used as a lateral etch stop material.Thus, lateral etching of the nearby dielectric layer may be furthermitigated by the lateral etch stopping functionality of the third metalmaterial 416. In some cases, the third metal material 416 is asacrificial layer which is removed at a subsequent processing step.

With reference now to FIG. 5, shown therein is a flow chart of asemiconductor manufacturing method 500, according to at least someembodiments. Additional steps may also be provided before, during, andafter the method 500, and some steps described can be replaced,eliminated, or moved before or after other steps for additionalembodiments of the method. It is also noted that the method 500 isexemplary, and is not intended to limit the present disclosure beyondwhat is explicitly recited in the claims that follow. The method 500will be further described below in conjunction with FIGS. 6A, 6B, 7A,7B, 8A, 8B, 9A, 9B, 10A, 10B, 11A, 11B, and 12A, 12B. FIGS. 6A, 7A, 8A,9A, 10A, 11A, and 12A show cross-section views of a FinFET structure 600along a plane substantially parallel to a plane defined by section CC′of FIG. 1, and FIGS. 6B, 7B, 8B, 9B, 10B, 11B, and 12B showcross-section views of the structure 600 along a plane substantiallyparallel to a plane defined by section AA′ of FIG. 1.

In various embodiments, the method 500 begins at block 502 where asubstrate including fins and isolation regions is provided. Withreference to the example of FIGS. 6A and 6B, and in an embodiment ofblock 502, the structure 600 is shown. The FinFET structure 600 mayinclude one or more of the features described above with reference tothe FIG. 1 such as fin elements 604 extending from a substrate,isolation regions 606, and a gate structure 608 disposed on and aroundthe fin-elements 604. In some embodiments, the fin-elements 604 may beformed as described above. A gate structure 608 may include a gate stackhaving a dielectric layer (e.g., including an interfacial layer and agate dielectric layer), and a metal layer formed over the dielectriclayer.

The method 500 proceeds to block 504 where a first work function metallayer is deposited. In some embodiments, the first work function metallayer includes a PWFM. Still referring to the example of FIGS. 6A and6B, and in an embodiment of block 504, a metal layer including a PWFMlayer 610 is formed over and around the fin-elements 604. Merely by wayof example, the PWFM layer 610 may include Ni, Pd, Pt, Be, Ir, Te, Re,Ru, Rh, W, Mo, WN, RuN, MoN, TiN, TaN, WC, TaC, TiC, TiAlN, TaAlN, orcombinations thereof. In various embodiments, the PWFM layer 610 may beformed using PVD, CVD, electron beam (e-beam) evaporation, and/or othersuitable process.

Thereafter, the method 500 proceeds to block 506 where a sacrificialmetal layer is deposited and a chemical mechanical polishing (CMP)process is performed. In some embodiments, the sacrificial metal layerincludes a tungsten (W) layer. In accordance with various embodiments,the sacrificial metal layer serves to mitigate lateral etching during asubsequent metal gate cut process, as described above. As shown in theexample of FIGS. 6A and 6B, and in an embodiment of block 506, asacrificial metal layer 612 is formed and a CMP process is performed toplanarize a top surface of the sacrificial metal layer 612. FIGS. 6A and6B also illustrate a plurality of gate stacks 615, which may have one ormore sidewall spacer layers 617 formed on sidewalls of the gate stacks615. The sidewall spacers may include a dielectric material such assilicon oxide, silicon nitride, silicon carbide, silicon oxynitride, orcombinations thereof. Moreover, in various embodiments, a dielectriclayer 619 may be interposed between each of the plurality of gate stacks615. In at least some embodiments, the sacrificial metal layer 612 mayserve to protect the dielectric layer 619 during a subsequent metal gatecut process.

The method 500 proceeds to block 508 where a hard mask layer isdeposited and patterned. In some embodiments, the hard mask layer mayinclude a patterned photoresist layer. Alternatively, in someembodiments, the hard mask layer may include a patterned dielectriclayer such as silicon nitride, silicon oxynitride, silicon carbide, orother suitable material. With reference to the example of FIGS. 6A and6B, a hard mask layer 614 is deposited. With reference to the example ofFIGS. 7A and 7B, the hard mask layer 614 is patterned. In someembodiments, the patterned hard mask layer 614 includes an opening 704that defines a metal gate line-cut to be performed later. For example,in some cases, the opening 704 may correspond to a metal gate cutpattern, similar to the metal gate cut pattern 210 of FIG. 2. In variousembodiments, a portion of the structure 600 over one of the gate stacks615 is exposed within the opening 704. In some embodiments, the opening704 has a larger width than a distance between adjacent sidewall spacersof the exposed gate stack 615. In some cases, this relaxes lithographyprocess resolution constrains for the metal gate line-cut process.

The method 500 proceeds to block 510 where a metal gate line-cut processis performed. With reference to the example of FIGS. 8A and 8B, and inan embodiment of block 510, a metal gate line-cut process is performed.As shown in FIGS. 8A and 8B, the line-cut process may be used to removeexposed portions of the sacrificial metal layer 612, including the PWFMlayer 610 thereunder, through the opening 704 to form a line-cut 804. Insome embodiments, the line-cut 8040 extends to the isolation regions 606and effectively separates conductive gate metal layers in adjacent gatestacks from one another. By way of example, an etch process used toperform the metal gate line-cut process of block 510 may include a wetetch, a dry etch, and/or a combination thereof. In some embodiments, theetch process is chosen to selectively etch the sacrificial metal layer612 and the PWFM layer 610 without substantially etching the sidewallspacers 617 and the dielectric layer 619. As described above, due to thethinner T2 (e.g., as compared to T1) of solely the PWFM layer 610 withinthe cut region, embodiments of the present disclosure may not requirethe significant over etching of the metal layers within the cut region,as is the case for at least some existing processes. Thus, loss (e.g.,via etching) of a nearby dielectric layer (e.g., the dielectric layer619) can be avoided. In some embodiments, after forming the line-cut804, the patterned hard mask layer 614 may be removed by an etchprocess. In some cases, where the patterned hard mask layer 614 is apatterned photoresist layer, the patterned hard mask layer 614 may beremoved by wet stripping and/or plasma ashing.

The method 500 proceeds to block 512 where a dielectric layer isdeposited and a CMP process is performed. With reference to the exampleof FIGS. 9A and 9B, and in an embodiment of block 512, a dielectriclayer 902 may be deposited and a CMP process is performed to planarize atop surface of the dielectric layer 902. In some embodiments, thedielectric layer 902 may include silicon oxide, silicon nitride,oxynitride, and/or other suitable dielectric material layer. Thus, invarious embodiments, the dielectric layer 902 may further serve toelectrically isolate gate metal lines of neighboring gate stacks.

In various cases, the method 500 then proceeds to block 514 where thesacrificial metal layer 612 is removed, as shown in the example of FIGS.10A and 10B. In various embodiments, the sacrificial metal layer 612 maybe removed by a wet etch, a dry etch, or a combination thereof. Afterremoval of the sacrificial metal layer 612, the method 500 proceeds toblock 516 where a second work function metal layer is deposited. In someembodiments, the second work function metal layer includes an NWFM.Referring to the example of FIGS. 11A and 11B, and in an embodiment ofblock 516, a metal layer including a NWFM layer 1110 is formed over thestructure 600. Merely by way of example, the NWFM layer 1110 may includeNi, Pd, Pt, Be, Ir, Te, Re, Ru, Rh, W, Mo, WN, RuN, MoN, TiN, TaN, WC,TaC, TiC, TiAlN, TaAlN, or combinations thereof. In various embodiments,the NWFM layer 1110 may be formed using PVD, CVD, electron beam (e-beam)evaporation, and/or other suitable process. In some embodiments, anetch-back process may be performed after formation of the NWFM layer1110.

In some embodiments, after forming the NWFM layer 1110, a glue layer maybe deposited over the NWFM layer 1110. In some embodiments, an etch-backprocess may be performed after formation of the glue layer. The method500 then proceeds to block 518 where a metal layer is deposited and aCMP process is performed. With reference to the example of FIGS. 12A and12B, and in an embodiment of block 518, a metal layer 1202 is formed anda CMP process is performed to planarize a top surface of the metal layer1202. In some embodiments, the metal layer 1202 includes a tungsten (W)layer. Alternatively, in some embodiments, the metal layer 1202 mayinclude other metals such as Ni, Pd, Pt, Be, Ir, Te, Re, Ru, Rh, W, Mo,WN, RuN, MoN, TiN, TaN, WC, TaC, TiC, TiAlN, TaAlN, or combinationsthereof. In embodiments including the glue layer deposited over the NWFMlayer 1110, the metal layer 1202 may be deposited on the glue layer.

The FinFET structure 600 may undergo further processing to form variousfeatures and regions known in the art. For example, subsequentprocessing may form various contacts/vias/lines and multilayersinterconnect features (e.g., metal layers and interlayer dielectrics) onthe substrate, configured to connect the various features to form afunctional circuit that may include one or more FinFET devices. Infurtherance of the example, a multilayer interconnection may includevertical interconnects, such as vias or contacts, and horizontalinterconnects, such as metal lines. The various interconnection featuresmay employ various conductive materials including copper, tungsten,and/or silicide. In one example, a damascene and/or dual damasceneprocess is used to form a copper related multilayer interconnectionstructure.

The various embodiments described herein offer several advantages overthe existing art. It will be understood that not all advantages havebeen necessarily discussed herein, no particular advantage is requiredfor all embodiments, and other embodiments may offer differentadvantages. For example, embodiments discussed herein include a metalgate cut process and related structure are provided. At least someembodiments of the present disclosure may be used to reduce inter-layerdielectric (ILD) loss during a metal gate cut process. For example, inat least some existing processes, over-etching of a metal gate layer(e.g., during a metal gate cut process) may lead to such undesirable ILDloss. To mitigate this issue, embodiments of the present disclosureprovide a metal gate layer, or multiple layers, having differentthicknesses on a fin (e.g., FinFET) and on a neighboring line-cutregion. Moreover, in at least some embodiments, a sacrificial metalportion may be used to prevent lateral etching during a metal line cutprocess, thereby effectively preventing ILD loss. Thus, embodiments ofthe present disclosure serve to overcome various shortcomings of atleast some current resist compositions and methods.

Thus, one of the embodiments of the present disclosure described amethod that includes forming a first fin and a second fin on asubstrate. In various embodiments, the first fin has a first gate regionand the second fin has a second gate region. By way of example, ametal-gate line is formed over the first and second gate regions. Insome embodiments, the metal-gate line extends from the first fin to thesecond fin, and the metal-gate line includes a sacrificial metalportion. In various examples, a line-cut process is performed toseparate the metal-gate line into a first metal gate line and a secondgate line. In some embodiments, the sacrificial metal portion preventslateral etching of a dielectric layer during the line-cut process.

In another of the embodiments, discussed is a method that includesforming a plurality of fin elements extending from a substrate. Invarious embodiments, each of the plurality of fin elements includes agate region, and a dielectric layer is disposed between each adjacentgate region. In some cases, a first work function metal layer isdeposited over the gate region of each of the plurality of fin elements.Thereafter, in some embodiments, a sacrificial metal layer is formedover the first work function metal layer. In some embodiments, afterforming the sacrificial metal layer, a cut region is defined using apatterned hard mask layer, where the patterned hard mask layer includesan opening corresponding to the defined cut region. In various examples,an etching process is then performed, through the opening in thepatterned hard mask layer, to remove the sacrificial metal layer and thefirst work function metal layer. In some embodiments, the sacrificialmetal layer prevents removal of the dielectric layer during theperforming the etching process.

In yet another of the embodiments, discussed is a semiconductor devicethat includes a first fin and a second fin extending from a substrate,the first fin having a first gate region and the second fin having asecond gate region. In some embodiments, the device also includes afirst metal layer disposed over the first gate region and along a firstsidewall of a first side of a dielectric layer, where the dielectriclayer is formed within a line-cut region. In addition, the device mayinclude a second metal layer disposed over the second gate region andalong a second sidewall opposite the first sidewall of a second side ofthe dielectric layer. In various embodiments, the first metal layer hasa first thickness over the first gate region, and the first metal layerhas a second thickness along the first sidewall of the first side of thedielectric layer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. A method of semiconductor device fabrication, comprising: forming afirst fin and a second fin on a substrate, the first fin having a firstgate region and the second fin having a second gate region; forming ametal-gate line over the first and second gate regions, wherein themetal-gate line extends from the first fin to the second fin, andwherein the metal-gate line includes a sacrificial metal portion; andperforming a line-cut process to separate the metal-gate line into afirst metal gate line and a second gate line, wherein the sacrificialmetal portion prevents lateral etching of a dielectric layer during theline-cut process.
 2. The method of claim 1, wherein the performing theline-cut process includes: forming a patterned hard mask over themetal-gate line, wherein the patterned hard mask defines an opening; andetching the metal-gate line through the opening.
 3. The method of claim1, wherein the sacrificial metal portion includes a sacrificial tungsten(W) layer.
 4. The method of claim 1, wherein the metal-gate lineincludes an N-type work-function metal (NWFM), and wherein the line-cutprocess is performed before deposition of the N-type work function metal(NWFM).
 5. The method of claim 1, wherein the metal-gate line includes aP-type work-function metal (PWFM), and wherein the line-cut process isperformed after deposition of the P-type work function metal (PWFM). 6.The method of claim 1, wherein the line-cut process includes a wet etchprocess.
 7. The method of claim 1, wherein the line-cut process forms aline-cut region having line-cut region sidewalls, wherein the metal-gateline has a first thickness over each of the first and second gateregions, and wherein the metal-gate line has a second thickness at eachof the line-cut region sidewalls.
 8. The method of claim 7, wherein thesecond thickness is less than the first thickness.
 9. The method ofclaim 7, wherein the metal-gate line includes both a P-typework-function metal (PWFM) and an N-type work-function metal (NWFM)deposited over each of the first and second gate regions, and whereinthe metal-gate line includes the N-type work-function metal (NWFM)deposited at each of the line-cut region sidewalls.
 10. A method,comprising: forming a plurality of fin elements extending from asubstrate, each of the plurality of fin elements including a gateregion, wherein a dielectric layer is disposed between each adjacentgate region; depositing a first work function metal layer over the gateregion of each of the plurality of fin elements; forming a sacrificialmetal layer over the first work function metal layer; after forming thesacrificial metal layer, defining a cut region using a patterned hardmask layer, wherein the patterned hard mask layer includes an openingcorresponding to the defined cut region; and performing an etchingprocess, through the opening in the patterned hard mask layer, to removethe sacrificial metal layer and the first work function metal layer,wherein the sacrificial metal layer prevents removal of the dielectriclayer during the performing the etching process.
 11. The method of claim10, further comprising: after performing the etching process, depositinga dielectric layer within a line-cut formed by the etching process; andremoving the sacrificial metal layer.
 12. The method of claim 11,further comprising: depositing a second work function metal layer overthe first work function metal layer and at least partially over asidewall of the dielectric layer deposited within the line-cut.
 13. Themethod of claim 12, further comprising: depositing a glue layer over thegate region of each of the plurality of fin elements; and forming ametal layer over the glue layer.
 14. The method of claim 10, wherein thefirst work function metal layer includes a P-type work-function metal(PWFM).
 15. The method of claim 12, wherein the second work functionmetal layer includes an N-type work-function metal (NWFM).
 16. Themethod of claim 10, wherein the patterned hard mask layer has a largerwidth than a distance between adjacent sidewall spacers of an exposedgate stack. 17-20. (canceled)
 21. A method, comprising: forming a firstgate region over a first fin and a second gate region over a second fin;depositing a P-type work-function metal (PWFM) over the first and secondgate regions, wherein the PWFM extends from the first fin to the secondfin; forming a sacrificial metal layer over the PWFM; and performing aline-cut process to separate the PWFM into a first metal gate line and asecond gate line, wherein the line-cut process forms a line-cut regionhaving line-cut region sidewalls; after performing the line-cut process,removing the sacrificial layer and depositing an N-type work-functionmetal (NWFM) over the PWFM in the first and second gate regions andalong each of the line-cut region sidewalls.
 22. The method of claim 21,wherein the sacrificial metal portion prevents lateral etching of adielectric layer during the line-cut process.
 23. The method of claim21, wherein a thickness of the NWFM disposed over the PWFM in each ofthe first and second gate regions is greater than a thickness of theNWFM disposed along each of the line-cut region sidewalls.
 24. Themethod of claim 21, wherein the sacrificial metal layer includes atungsten (W) layer.